How do you allow an object to rotate around an axis?
I believe it would be easier to animate it, use shift + axis.

add a key-frame where it should start with the desired rotation, and then add other key frames where you want the 'fan' to turn and the angle of choice. (i chosen 359 because im not sure if i set it to 360 it would just not move, but go ahead and experiment! )


blender will automatically interpolate the key frames you set.

but if you really want accurate physics then im afraid i also don't know :(

but maybe this post will help.